The hepatitis C virus (HCV) is a major worldwide public health problem affecting an estimated 120-170 million people. Unfortunately, an effective vaccine for HCV does not yet exist and current therapies are toxic and variably effective. While much has been learned about HCV pathogenesis, the virus and host factors that influence spontaneous clearance or persistent infection remain unknown. The lack of robust in vitro and in vivo models that faithfully mimic natural HCV infection of humans continues to hamper studies of HCV pathogenesis. Though hepatocellular carcinoma derived cell lines and immortalized hepatocytes allow us to study the replication of HCV, they are phenotypically and functionally abnormal as compared to primary hepatocytes. While primary hepatocyte cultures are thought to be an ideal model to study HCV infection and virus/host interactions, their liver specific functions rapidly decline in conventional culture systems. Recently, the creation of bioengineered micropatterned co-cultures (MPCCs) of hepatocytes and fibroblasts have allowed for long term culture of hepatocytes with the retention of normal cell function (albumin production, urea synthesis etc). The long-term goal of our research is to gain a better understanding of HCV pathogenesis in order to design specific and effective therapeutics. We hypothesize that early virus and host interactions influence the outcome of disease setting the stage for spontaneous clearance or chronic infection/liver fibrosis. To gain insight into early host response to acute HCV infection in the liver, we propose to characterize HCV virus/host interactions within primary human hepatocyte MPCCs and in MPCCs of increasing cellular complexity. Under specific aim 1, we will differentially phenotype infected and non-infected cells within MPCCs performing both genomic and proteomic profiling to identify host genes and pathways modulated in HCV infection. In specific aim 2, we will increase the cellular complexity of MPCCs to include non-parenchymal cells in order to assess if supporting cell types in the liver contribute to HCV pathogenesis and/or the development of a profibrotic state. In specific aim 3, we will increase the cellular complexity of MPCCs to include lymphocytes resident or recruited to the liver during HCV infection in order to assess the effects of immune cells on acute HCV infection. Through the use of the novel MPCCs, we may gain a better understanding of HCV pathogenesis, which may guide the development of rationally designed antiviral therapies. The development of effective HCV antivirals or vaccines would have a profound impact on global public health.